In the conventional drilling of an oil and gas well, a series of drill pipe joints (each joint approximately 30 feet in length) are connected together to form the drill string used in the drilling of a well bore. As the drilling operation proceeds, more and more drill pipe joints must be connected together and lowered into the borehole. For deeper wells, it may be necessary to connect literally hundreds of pipe joints together to drill the well bore to the depth of the producing zone.
The drill pipe joints are typically coupled together using threaded connections, known as tool joints, in which the male end, or pin member, of one pipe joint is threadably connected to the female end, or box member, of an adjacent pipe joint. The process of threadably coupling adjacent pipe joints together is a time consuming process that requires a significant amount of pipe handling by the drilling rig's crew.
Specifically, in a typical rotary table drilling operation, a drill bit is placed on the downward end of the drill string. Drill collars—which are essentially thick-walled sections of drill pipe—are connected together to form the bottom hole assembly section of the drill string. The drill collars are used to provide sufficient weight on the drill bit as the drill bit is rotated in the borehole to drill deeper. To rotate the drill string in the borehole, a top drive unit may be used to provide the rotational force to the drill string. Top drive units are connected between the swivel and the crown block in the mast.
Each time drilling has proceeded far enough to require that a new drill pipe joint be added to the drill string, it is necessary (1) to stop rotation of the drill string, (2) to support the drill string in the borehole, as with slips, (3) to detach the top drive from the upper pipe joint of the drill string, (4) to attach the top drive to the upper end of a new pipe joint to be added to the drill string, and (5) to make-up the threaded connection between the upper joint of the drill string and the new joint of drill pipe—through use of manually operated tongs or an iron roughneck. Once the new pipe joint has been added to the drill string, the drill string is rotated again and drilling is resumed. As the borehole depth increases, the process of adding a new joint of drill pipe is repeated until the drill string reaches the desired well bore depth.
As the general description above shows, rotation of the drill string (and, thus, drilling of the borehole) must cease and the rotating equipment must be disconnected from the drill string in the borehole each time it is necessary to make-up a new joint of drill pipe to the drill string. The making-up of the drill string is thus a time consuming process that limits the amount of new hole that can be drilled in a single day. Given the expense of drilling operations, it is desirable, and in the case of a deep well essential, to minimize the time required to drill the well bore.
Further, it should be noted that the making-up of the drill string requires a substantial amount of drill pipe handling by the drilling rig crew. Given the equipment used to make-up the drill string, the size and weight of the pipe joints used, and the time pressure under which the drilling crew operates, the substantial amount of pipe handling required to drill the well bore provides ample opportunity for injury to the drilling rig personnel.
In an effort to reduce the amount of time required to make-up the drill string and, ultimately, to drill the well bore, drilling rig manufacturers have begun to design rigs with the ability to make-up “stands” of drill pipe “off-line”—i.e., to make-up joints of drill pipe with equipment other than the main drilling equipment. These drill pipe stands typically consist of two, three, or even four pipe joints threadably connected together. The size of the drill pipe stands that can be assembled off-line is primarily dependent on the size of the drilling rig's mast or derrick (hereinafter collectively referred to as “mast”).
After being assembled, these stands can be stored in racking boards attached to and extending outwardly from the drilling rig's mast. When additional pipe joints are needed for continued drilling operations, these pipe stands can be connected to the drill string. In this way, two, three, or four additional pipe joints can be connected to the drill string through a single make-up using the main drilling equipment.
Although prior art off-line pipe make-up systems provide the ability to make-up stands of drill pipe off-line, the prior art systems still require a significant amount of pipe handling by the drilling rig crew. The prior art systems typically require two “off-line holes”, equivalent to the mousehole in the drilling rig, for placement of the drill pipe joints prior to make-up. Specifically, in the prior art systems, a first joint of drill pipe is lifted from the V-door ramp of the drilling rig and placed in a first off-line hole in a platform attached to the drilling rig that supports an off-line roughneck. A second joint of drill pipe is then lifted from the V-door ramp and placed in a second off-line hole in the off-line roughneck platform. A third joint of drill pipe is then lifted from the V-door ramp and swung into engagement with the first joint of drill pipe—which is positioned in the off-line hole closest to the offline roughneck. The two joints are then made up using the off-line roughneck, lifted above the off-line roughneck, and swung into position above the third pipe joint. In similar fashion, the two connected joints are made up with the third joint in the second off-line hole. The drill pipe stand is then lifted from the off-line roughneck and positioned in a racking board for subsequent use.
As the preceding general description shows, the prior art off-line make-up systems require a significant amount of pipe handling by the drilling rig's crew. Further, the prior art systems require off-line holes that are potential hazards to the rig crew performing the off-line make-up operations.
The present invention is designed to address these and other known problems with the prior art systems. What is needed is an apparatus and method for off-line make-up of drill pipe stands that allows for less pipe handling by a drilling rig's crew and, thus, allows for a safer and more efficient off-line make-up operation. It is an object of the present invention to provide such an apparatus and method for off-line make-up of drill pipe stands. Those and other objectives will become apparent to those of skill in the art from a review of the specification below.